High-harmonic generation by focusing a femtosecond laser onto a gas is a well-known method of producing coherent extreme-ultraviolet (EUV) light. This nonlinear conversion process requires high pulse intensities, greater than 10(13) W cm(-2), which are not directly attainable using only the output power of a femtosecond oscillator. Chirped-pulse amplification enables the pulse intensity to exceed this threshold by incorporating several regenerative and/or multi-pass amplifier cavities in tandem. Intracavity pulse amplification (designed not to reduce the pulse repetition rate) also requires a long cavity. Here we demonstrate a method of high-harmonic generation that requires no extra cavities. This is achieved by exploiting the local field enhancement induced by resonant plasmons within a metallic nanostructure consisting of bow-tie-shaped gold elements on a sapphire substrate. In our experiment, the output beam emitted from a modest femtosecond oscillator (100-kW peak power, 1.3-nJ pulse energy and 10-fs pulse duration) is directly focused onto the nanostructure with a pulse intensity of only 10(11) W cm(-2). The enhancement factor exceeds 20 dB, which is sufficient to produce EUV wavelengths down to 47 nm by injection with an argon gas jet. The method could form the basis for constructing laptop-sized EUV light sources for advanced lithography and high-resolution imaging applications.

A simple colorimetric technique for the detection of small concentrations of aqueous heavy metal ions, including toxic metals such as lead, cadmium, and mercury, is described. Functionalized gold nanoparticles are aggregated in solution in the presence of divalent metal ions by an ion-templated chelation process; this causes an easily measurable change in the absorption spectrum of the particles. The aggregation also enhances the hyper-Rayleigh scattering (HRS) response from the nanoparticle solutions, providing an inherently more sensitive method of detection. The chelation/aggregation process is reversible via addition of a strong metal ion chelator such as EDTA. Suggestions for improving the sensitivity and selectivity of the technique are given.

An amorphous red phosphorus/carbon composite is obtained through a facile and simple ball milling process, and its electrochemical performance as an anode material for Na ion batteries is evaluated. The composite shows excellent electrochemical performance including a high specific capacity of 1890 mA h g(-1), negligible capacity fading over 30 cycles, an ideal redox potential (0.4 V vs. Na/Na(+)), and an excellent rate performance, thus making it a promising candidate for Na ion batteries.

Vision and language understanding has emerged as a subject undergoing intense study in Artificial Intelligence. Among many tasks in this line of research, visual question answering (VQA) has been one of the most successful ones, where the goal is to learn a model that understands visual content at region-level details and finds their associations with pairs of questions and answers in the natural language form. Despite the rapid progress in the past few years, most existing work in VQA have focused primarily on images. In this paper, we focus on extending VQA to the video domain and contribute to the literature in three important ways. First, we propose three new tasks designed specifically for video VQA, which require spatio-temporal reasoning from videos to answer questions correctly. Next, we introduce a new large-scale dataset for video VQA named TGIF-QA that extends existing VQA work with our new tasks. Finally, we propose a dual-LSTM based approach with both spatial and temporal attention, and show its effectiveness over conventional VQA techniques through empirical evaluations.

Sn4 P3 is introduced for the first time as an anode material for Na-ion batteries. Sn4 P3 delivers a high reversible capacity of 718 mA h g(-1), and shows very stable cycle performance with negligible capa-city fading over 100 cycles, which is attributed to the confinement effect of Sn nanocrystallites in the amorphous phosphorus matrix during cycling.

This review summarises smart thermo-responsive polymeric materials with reversible and ‘on–off’ remotely switchable properties for a wide range of biomedical and biomaterials applications.

Ultrashort extreme-ultraviolet pulses are a key tool in timeresolved spectroscopy for the investigation of electronic motion in atoms 1,2 , molecules 3 and solids 4 . High-harmonic generation is a well-established process for producing ultrashort extreme-ultraviolet pulses by direct frequency upconversion of femtosecond near-infrared pulses [5][6][7] . However, elaborate pump-probe experiments performed on the attosecond timescale 8,9 require continuous efforts to improve the spatiotemporal coherence and also the repetition rate of the generated pulses. Here, we demonstrate a three-dimensional metallic waveguide for the plasmonic generation of ultrashort extreme-ultraviolet pulses by means of field enhancement using surface-plasmon polaritons. The intensity enhancement factor reaches a peak of ∼350, allowing generation up to the 43rd harmonic in xenon gas, with a modest incident intensity of ∼1 3 10 11 W cm -2 . The pulse repetition rate is maintained as high as 75 MHz without external cavities. The plasmonic waveguide is fabricated on a cantilever microstructure and is therefore suitable for near-field spectroscopy with nanometre-scale lateral selectivity.Surface-plasmon polaritons (SPPs) are described as the electromagnetic wave propagating along a metal-dielectric interface that results from coupling between incident photons and surface plasmons 10,11 . In nanostructured tapered waveguides, SPPs can be controlled to adiabatically follow the geometric shape of the waveguide and asymptotically stop at the tip of the taper where the local crosssectional dimension becomes infinitesimally small 12,13 . As a result, SPPs can be focused beyond the diffraction limit in three dimensions on a sub-wavelength spot, with drastically enhanced optical intensity [12][13][14] . The effect of SPP adiabatic nanofocusing has been confirmed, studied and also tested for nanometre-scale microscopy in a series of earlier experiments [15][16][17][18][19] .In our investigation, this intriguing phenomenon of SPP adiabatic nanofocusing is used to generate ultrashort extreme ultraviolet (EUV) pulses directly from near-infrared (NIR) pulses. As depicted in Fig. 1, a three-dimensional waveguide was devised to concentrate the incident NIR pulses into a sub-wavelength spot, allowing highharmonic generation of EUV light pulses to take place with high spatiotemporal coherence. The waveguide is a metallic nanostructure made of silver and has a hollow hole that takes the shape of a tapered cone with its elliptical cross-section decreasing from the inlet aperture (minor-axis diameter, 2 mm) to the exit aperture (minor-axis diameter, 100 nm). The incident NIR pulses are focused on the inlet aperture at a repetition rate of 75 MHz with a moderate intensity of 1 × 10 11 W cm 22 . While each NIR pulse propagates through the tapered hole towards the exit aperture, the electric field intensity inside the hole undergoes a substantial boost that is sustained by the SPPs driven by the incident NIR pulse. Consequently, high-harmonic EUV pulses are generate...

A smart hyperthermia nanofi ber is described with simultaneous heat generation and drug release in response to 'on-off ' switching of alternating magnetic fi eld (AMF) for induction of skin cancer apoptosis. The nanofi ber is composed of a chemically-crosslinkable temperature-responsive polymer with an anticancer drug (doxorubicin; DOX) and magnetic nanoparticles (MNPs), which serve as a trigger of drug release and a source of heat, respectively. By chemical crosslinking, the nanofi ber mesh shows switchable changes in the swelling ratio in response to alternating 'on-off ' switches of AMF because the self-generated heat from the incorporated MNPs induces the deswelling of polymer networks in the nanofi ber. Correspondingly, the 'on-off ' release of DOX from the nanofi bers is observed in response to AMF. The 70% of human melanoma cells died in only 5 min application of AMF in the presence of the MNPs and DOX incorporated nanofi bers by double effects of heat and drug. Taken together these advantages on both the nano-and macroscopic scale of nanofi bers demonstrate that the dynamically and reversibly tunable structures have the potential to be utilized as a manipulative hyperthermia material as well as a switchable drug release platform by simple switching an AMF 'on' and 'off '.